Lifter roof storage tank



Feb. 21, 1950 J. w. ALLEN LIFTER ROOF STORAGE TANK 2 Sheets-Sheet 1 Filed Sept. 13, 1945 Feb. 21, 1950 J, w, ALL N 2,497,851

LIFTER ROOF STORAGE TANK Filed Sept. 13, 1945 I 2 Sheets-She et 2 Patented Feb. 21, 1950 UNITED STATES PATENT OFFICE LIFTER ROOF STORAGE TANK John W. Allen, Chicago, 111., assignor to Chicago Bridge & Iron Company Application September 13, 1945, Serial No. 615,943

11 Claims. 1

This invention relates to a lifter roof type :tOlgge tank, and particularly to a roof for said Storage tanks of the lifter roof type are used for storing liquids or gases, and the roof is raised or lowered by pressure of the contents of the tank. Various means have been proposed for sealing the edge of the roof to the inner surface of the tank shell so that the contents will not escape, but many of the structures have been unsatisfactory. In some tanks the seal interfered with movement of the roof, while in others the seal wore out and permitted the tanks contents to leak out.

I have invented a lifter roof for a storage tank that employs a flexible seal between the edge of the roof and the inner surface of the tank shell. This flexible shell is so constructed that the only wear is due to bending, as it does not rub against itself or against the roof and the tank shell when the roof is changing positions. This new roof is also provided with a counterweight which balances the roof against tipping action of any external loads such as wind and snow. This counterweight also balances at least part of the weight of the roof, causing a reduced operating pressure. The counterweight is attached to the tank shell by a cable means running over at least one sheave that is attached to the roof. The counterweight is preferably connected to the tank shell by a plurality of cable means substantially equally spaced around the tank. The counterweight system may be applied to any movable piston-like object although it will be specifically described as applied to the new lifter roof.

The invention will be described as related to a typical embodiment as shown in the accompanying drawings. Of the drawings Fig. 1 is a plan view of the tank; Fig. 2 is a vertical section taken along line 2-2 of Fig. 1 with the roof of the tank in its lowest position; Fig. 3 is a view similar to Fig. 2 with the roof in its highest position; Fig. 4 is an enlarged fragmentary elevation showing a section of the top center of the tank; and Fig. 5 is an enlarged fragmentary elevation showing the top edge of the tank.

The storage tank illustrated in the accompanying drawings includes an outer shell Ill of cylindrical shape and a lifter roof I I of substantially circular shape located within the shell and extending beyond the sides thereof. Attached to the roof is a vertical cylindrical inner skirt l2 extending down from the roof and within the shell I0. At the outer edge of th roof II there is located a downwardly extending cylindrical 2 weather skirt I3 on the outside of the shell. This weather skirt is to prevent rain from being blown into the seal. On top of the outer shell II] there is located a narrow cylindrical back up shell I4 with its lower edge abutting the top edge of the shell ID.

A flexible seal I5 is provided between the roof II and the shell I 0 of the tank. This flexible seal may be a fabric impregnated with a flexible impervious material such as a synthetic rubber. An excellent synthetic rubber for this purpose is neoprene. The back up shell serves to reinforce the flexible seal when the roof II is in its top position.

The seal I5 is bolted at one edge to the bottom of the inner skirt I2, and at the other edge is bolted between the back up shell I 4 and the main shell Ill. The seal extends all around the tank and is wider than the distance between the lines of attachment when this distance is at a maximum. Thus the seal I5 is bowed upward at all times by the pressure of the contents of the tank. Because of this pressure the seal is never permitted to rub against itself as the roof changes positions, and likewise does not rub against the roof or the seal. The arrangement of the seal at the lowest position of the roof is shown in Fig. 2, and its arrangement at the highest position is shown in Fig. 3.

A counterweight I6 is attached to the shell I0 by means of cables I! which pass over sheaves attached to the roof. These cables are substantially equally spaced around the tank and not less than three should be used on any tank. In the embodiment shown six cables are provided.

The counterweight I6 is of cylindrical shape and is housed in a cylindrical well I8 located at substantially the center of the tank and extending through a hole I9 in the center of the roof. The well I8 is supported on the bottom of the tank by a post 20. The well I8 and post 2B are reinforced against lateral movement by means of a plurality of rods 2| extending radially to the shell II] of the tank. The rods are attached at their inner ends to a circular bearing plate 22 located on the bottom of the well and against which the post 20 bears.

The space between the well I8 and the hole I9 in the center of the roof is sealed by means of a second flexible seal 23. This seal extends around the opening and is also made of a fabric impregnated with an impervious flexible material such as neoprene. It is wider than the greatest distance between its points of attachment to the well I8 and to the edge of the hole I9. The

sheaves over which it is extended to the side of the shell. Each cable extends from the counterweight l6 over a first sheave 25 fastened to the top of the well l8. under a second sheave 26 attached to the roof adjacent the well, over a third sheave 2'! attached to the edge of the roof, down over a fourth sheave 28 located beneath the third sheave 21 and attached thereto and to the roof by means of an angular bracket 29. From the fourth sheave 28 the cable extends upward to the tank shell and is attached thereto by means of a semicircular eye 3H attached to the shell. The second sheave 26 holds the cable I! adjacent the roof ll.

When the lifter roof is in its lowest position it is supported by means of a shelf 3| fastened to the inside of the shell l and a second shelf 32 fastened to the outs de of the wel l8. The roof is supported on the first shelf 3| by the inner skirt I2. surface adjacent the hole I9 surrounding the well l8.

The counterweight system shown and described helps limit pressure on the two flexible seals but its principal purpose is to stabilize the roof and keep it level. If the roof is forced down at one point the strain on the cables adjacent this point becomes greater, and this tends to pull the roof back into position.

In the construction shown in the accompanying drawings the mechanical efficiency of the counterweight and cable system is approximately two when the roof is in an intermediate position between top and bottom. When the roof is near its top position the eificiency is less than two but greater than one. Any mechanical efliciency may be provided by altering the number of sheaves attached to the roof and by changing the point of attachment of each cable to the shell.

The weight of the counterbalance may be equal to or less than the weight of the roof, depending upon the pressure desired in the storage tank. It will not ordinarily be greater than the weight of the roof.

Although the counterweight system has been described in detail as applied to a lifter roof the same system may be applied to any movable piston-like object located in a housing and movable relative thereto. The system has the advantage of stabilizing the object to keep it level and also will balance at least a portion of the weight of the object.

The storage tank shown and described may be used for storing liquids as well as gases. When the tank is to be used for storing liquids the roof will float on top of the liquid without the provision of pontoons, although their use is not preeluded.

Having described my invention as related to a typical embodimentof the same, it is my intention that the invention be not limited by the details of description unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying ;claims.

The second shelf 32 contacts the roof at a I claim:

1. A storage tank comprising an outer shell, a lifter roof raised and lowered within the circumference of the shell wall by the pressure of the gas within the tank, an annular seal comprising a fabric impregnated with an impervious flexible material having one edge attached to the edge of the roof and having its other edge attached to the shell along a substantially horizontal line around the interior of the shell near the top thereof, the width of said seal between its edges be'ng greater than the distance between the edge of the roof and said line in all positions of the roof whereby the seal is at all times bowed upward by pressure of the contents of the tank, and a counterweight vertically movable in a stationary well at the center of the tank and attached through a cable means to the shell, said cable means including at least two cables, with each cabe extending around a plurality of sheaves and passing under at least one sheave attached to the roof, and a flexible seat between the roof and the 'el.

2. A storage tank comprising an outer shell, a l fter roof raised and lowered within the circumference of the shell wall by the pressure of the gas within the tank, a flexible seal between the outer edge of the roof and the shell, a counterweight at sub-tantially the center of the tank attached through a cable means to the shell, said cabe means including at least two cables, with each cable extending around a plurality of sheaves and passing under at least one sheave attached to the roof, a stationary well for housing the counterbalance extending through the roof at substantially the center thereof, and a flexible seal between the well and the center portion of the roof that surrounds the well.

3. The storage tank of claim 2 wherein the seal around the well comprises a fabric impregnated with an impervious flexible material with said seal being wider than the distance between its two points of attachment at all positions of the roof whereby the seal is at all times bowed upward by pressure of the contents of the tank.

4. The storage tank of claim 2 wherein both said seals comprise fabric impregnated with impervious flexible material, said seals being wider than the distances between their respective points of attachment at all positions of the roof whereby the seals are at all times bowed upward by pressure of the contents of the tank.

5. A storage tank comprising an outer shell, a lifter roof raised and lowered within the circumference of the shell wall by the pressure of the gas within the tank, an annular seal comprising a fabric impregnated with an impervious flexible material having one edge attached to the edge of the roof and having its other edge attached to the shell along a substantially horizontal line around the interior of the shell near the top thereof, a counterweight positioned in a stationary well at substantially the center of the tank with the well extending through the roof, a sec 0nd seal comprising a fabric impregnated with an impervious flexible material extending from the well to the center portion of the roof surrounding the well, both said seals being wider than the distance between their respective points of attachment at all positions of the roof. and a plurality of cables each extending from the counterweight to the outside of the shell around a plurality of sheaves and passing under at least one sheave attached to the roof.

6. The storage tank of claim 5 wherein the cables are substantially equally spaced around the tank.

7. The storage tank of claim wherein the counterweight is substantially cylindrical and the well is also substantially cylindrical and supported on the floor of the tank.

8. The storage tank of claim 5 wherein each cable extends from the counterweight over a sheave attached to the top of the well, over a second sheave attached to the edge of the roof, down under a third sheave located below the second one and also attached to the root, and then to a point on the exterior of the tank shell.

9. The storage tank of claim 5 wherein the cables are substantially equally spaced around the tank and each cable extends from the counterweight over a sheave attached to the top of the well, over a second sheave attached to the top of the roof, down under a third sheave located below the second one, and also attached to the roof, and then to a point on the exterior of the tank shell.

10. The storage tank of claim 5 wherein the cables are substantially equally spaced around the tank and each cable extends from the counterweight over a sheave attached to the top of the well, under a second sheave attached to the root near the well, over a third sheave attached to the outer edge oi the roof, down under a fourth sheave located below the third one and also attached to the roof, and then to a point on the exterior of the tank shell, said third and fourth sheaves extending beyondthe edge of the tank shell.

11. A counterweight system for a movable piston or the like comprising a piston, a housing around the piston with said piston movable ver tically therein, a weight located substantially in the center of the piston and movable vertically relative thereto, a guide housing at the center of the piston and stationary relative to the piston housing, around a third sheave attached to the outer edge of the piston, under a fourth sheave f located below the third and also attached to the piston, and finally to the side of the piston housing.

JOHN W. ALLEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,911,462 Neal May 30, 1933 2,436,348 Allen .4 Feb. 17, 1948 FOREIGN PATENTS Number Country Date 4,790 Great Britain of 1823 453,238 Germany Dec. 1, 1927 Certificate of Correction Patent No. 2,497,851 February 21, 1950 JOHN W. ALLEN It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 22, for the word seat read seal;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 4th day of July, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

